if alpha, beta and gamma are the roots of
the equation x^3 - 4x^2+6X-4 = 0.
the value of 1/alpha + 1/beta + 1/gamma is .
Answers
Answer:
The value of ( 1/alpha + beta) + (1/beta + gamma) + (1/alpha + gamma) is 2
Solution:
Given that, f(x)=x^{3}+4 x+2f(x)=x
3
+4x+2
On comparing it with general Equation a x^{3}+b x^{2}+c x+dax
3
+bx
2
+cx+d we get,
a = 1, b = 0 , c = 4 and d = 2
\text {Also, } \alpha, \beta, \gamma \text {are the zeroes of the given cubic polynomial }Also, α,β,γare the zeroes of the given cubic polynomial
\text {Sum of zeroes of cubic polynomial }=\frac{-b}{a}Sum of zeroes of cubic polynomial =
a
−b
\alpha+\beta+\gamma = \frac{-0}{1}=0α+β+γ=
1
−0
=0 ---- eqn 1
\text {Sum of product of two zeroes of cubic polynomial }=\frac{c}{a}Sum of product of two zeroes of cubic polynomial =
a
c
\alpha \times \beta+\beta \times \gamma+\gamma \times \alpha=\frac{4}{1}=4α×β+β×γ+γ×α=
1
4
=4
\text {Product of zeroes of cubic polynomial }=\frac{-d}{a}Product of zeroes of cubic polynomial =
a
−d
\alpha \times \beta \times \gamma=\frac{-2}{1}=-2α×β×γ=
1
−2
=−2
We need to find value of :-
\frac{1}{\alpha+\beta}+\frac{1}{\beta+\gamma}+\frac{1}{\gamma+\alpha}
α+β
1
+
β+γ
1
+
γ+α
1
From equation (1), we get
=\frac{1}{-\gamma}+\frac{1}{-\alpha}+\frac{1}{-\beta}=
−γ
1
+
−α
1
+
−β
1
=\frac{-(\alpha \times \beta+\beta \times \gamma+\gamma \times \alpha)}{\alpha \times \beta \times \gamma}=
α×β×γ
−(α×β+β×γ+γ×α)
Subsituting the values we get,
=\frac{-(\alpha \times \beta+\beta \times \gamma+\gamma \times \alpha)}{-2}=
−2
−(α×β+β×γ+γ×α)
=\frac{-(4)}{-2}=2=
−2
−(4)
=2
Hence the value is found as 2
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